Electrical transmission system



Nov. 11, 1930. P. w. BLYE ELECTRICAL TRANSMISSION SYSTEM Filed March 11926 Fansforvpens 7', and 7;, have men cares.

INVENTOR Z? WBZye ATTORNEY Patented Nov. 11, 1930 UNITED STATES PATENTOFFICE PAUL W. BLYE, OF RUTHERFORD, NEW'JERSEY, ASSIGNOR TO AMERICANTELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK ELECTRICALTRANSMISSION SYSTEM Application filed March 1, 1926. Serial No." 91,628.

This invention relates to electrical transmission systems, andparticularly to arrangements in such systems for transmitting thefundamental frequency of a source to a receiving circuit through atransformer without the introduction of harmonics of the fundamentalfrequency by the transformer.

In systems for the transmission of a fundamental frequency of a sourceto an output or receiving-circuit, it is often necessary to isolate theoutput or receiving circuit from the source of fundamental frequency bymeans of a transformer interconnecting the source of current and theoutput or receiving circuit. The transformer will of itself generateharmonics which will also be transmitted to the output or receivingcircuit along with the fundamental frequency. In systems in which thewave shape of the current in a source is to be faithfully reproduced inan output or receiving circuit, it is very often necessary to providearrangements for eliminating or minimizing the effect of these harmonicson the wave shape of the current of the source. 7 I I Accordingly, it isan object of this invention to provide arrangements in a system in whichatransformer interconnects a source of fundamental frequency and anoutput circuit for eliminating the harmonics of the fundamentalfrequency generated in the transformer.

It is another object of this invention to isolate a source of currentfrom an output or receiving circuit by means of transformers in such amanner as to eliminate the harmonies or other currents Which might beintroduced by the transformers.

It is another object of this invention to provide arrangements forbalancing the harmonics of a fundamental frequency introduced by atransformer by harmonics of equal magnitude and of opposite phase.

While the invention will be defined in the appended claims, the furtherobjects and features of the invention will be better understood from thedetailed description hereinafter following when read in connection withthe accompanying drawing showing one em bodiment of the invention.

Referring to the drawing, a transformer T is shown having a'primarywinding 1 and secondary winding 2. The transformer T isolates an outputor receiving circuit connected to the leads 3 from a source of currentof fundamental frequency connected to the leads 4:. A second transformerT having a secondary winding 5 and a primary winding 6 is so related tothe transformer T as to balance out harmonics generated in' the firsttransformer, as will be better understood from the descriptionhereinafter f0llowing. The secondary windings of the transformer T and Twhich may preferably have the same constants, are interconnected througha variable resistance 7 in the circuit including the secondary winding 2of the transformer T the secondary winding 5 of the transformer T andthe variable resistance 7. Three resistances 8, 9 and 10 are in serieswith the source of current connected to the leads/l, the resistance 9being bridged across a primary winding 1 of the transformer T Theseresistances 8, 9 and 10 are used to eliminate the effect of theimpedance of the source of current connected to the leads l on theoutput or receiving circuit connected to the leads 3. An adjustableimpedance 11 is bridged across the primary winding 6 of the transformerT Current from the source connected to the leads 4 passes through theresistances 8, 9 and 10, effecting a drop in potential across theresistance 9. Due to the relationship existing between the primarywinding 1 of the transformer T and the resistance 9, the current fromthe source will also be impressed upon the primary winding 1 of thetransformer T As is well known in the art, harnonics of a fundamentalfrequency of the source will be introduced'by the transformer T theseharmonics having the values of I amperes and I amperes in the primaryand secondary circuits, respectively. Similarly, the application of thefundamental frequency to the transformer T results in the circulation ofharmonics of the fundamental fre quency in the primary and secondarycircuits of the transformer T these harmonics being generated in thetransformer T and having the values of L amperes and I amperes in theprimary and secondary circuits of the transformer T respectively.

The voltage of the fundamental frequency induced in winding 2 oftransformer T is substantia lly in phase oppos'itionto "the yolt age ofthat frequency impressed upon winding 1. Due to the nonlinear hysteresischaraeteristlcsof the iron core of transformer T harmonic voltagesare-generated in windings 1 and 2, the voltages in winding 2 bear ing adefinite phase relation to" the voltage of the fundamental frequency inwinding 2 The voltage of the fundamental' frequency in winding 2alsobecomes impressed upon wind,- ing 5' of transformer T As in the case oftransformer T harmonic voltages are similarly" generated in both;windings 5V and 6 of transformer T The harmonic voltages induced inwinding 5 will have the same phase relationtojthe current of thefundamental frequencyasthe harmonic voltages inwindi-ng 2 had'to thecurrent of the funda- 7 mental frequency in the latter winding. Theharmonic voltages generated in transformers T and T willcause'harmoniccurrents to circulate in the attached circu ts. as

' indicated by the arrows adjacent to the ref- Since erence characters II L, and T the harmonic voltages induced in winding 2 bearstthe" samephase relation to the fundamental voltage in winding 2 as the harmonicvoltages generated in winding 5 bear to the 4V fundamental voltageapplied to winding5, then in the local circuit, including windings 2 and5 and resistance7,the two sets'of harm'onicvolta'ges will result incurrents I and I which are substantially in phase opposiw tion.

' The.variableresi'stance '7 is included in a seriescircuit 'with thesecondary winding 2 of the transformer T and the secondary winding 5 ofthe transformer T For a given valueof resistance 7, by adjus'tingtheimpedance 11, theh'a'rm'onics'of the fundamental frequencyfI" amperesand L/famperes, in the secondary winding 2 of the transformer T and inthe secondarywinding 5 of the trans former T respectively, may be madeequal in magnitude and opposite in phase. Consequently, when thisadjustment is made, the harmonics of the fundamental frequency generatedin the secondary winding 2 of transformer T will be neutralized by thehar stantially free from harmonics generated in either transformer.

It will be understood, however, that the harmonics generated in thetransformer T may be balanced or neutralized by equalharmonics'generated by an iron core inductance coil of the proper sizeif placed in the circuit in the position of the transformer T inparallel relationshipwith-impedance}1. i

While the invention has been'disc'losed 1117.; one particularembodiment,'which is deemed desirable, it is to be understood that it iscapable of embodiment in other and widely varied organizations withoutdeparting from the spirit of the invention or the scope of the appendedclaims;

What is claimed is: r r

'1". The method of eliminating the harmonics of a fundamental frequencygenerated in a transformer connected'to a source of as fundamentalfrequency with apparatus including second transformer, whichconsists ingenerating the same harmonics in the second transformer, andbalancingoutthese harmonies without affecting thezfundamental 913'frequency. v

v2. A system for eliminating the harmonics of a-fundamental frequencygeneratedby a two-winding transformer connected to a source of thefundamentalfrequency, comprising'a second two-winding transformer, meansfor generating the same harmonics in the second transformer, and meansforbalancing out these harmonics without affecting the fundamentalfrequency.

"3. A system for eliminating the harmonics generated in a transformerconnected to a source of fundamental frequency compris ing a secondtransformer, each of'said trans= n formers having first andsecond'windings, a resistance, and means for generating in the secondtransformer harmonics of the funda-- mental frequency which are equal inmagni tude and opposite inph'ase to those harmonics generated in thetransformer connected to the source" of fundamental frequency,the secondwindings of the transformers being arranged in a series circuitwith theresistance. 4; In combinatioina source of fundamentalfrequency,twotransformers each having first and'second windings,th'e'first winding of one of said transformers being connectedto' thesource of fundamental frequency, and an adjustable resistance, thesecond windingsvof said transformers'being connected to the re-'sistance in alocal circuit, the resistance being adjusted so that thecurrents of the har monies of the fundamental frequency gener areatherein are equal in magnitude and opposite in phase.

' '5. A system'forcfaithfully reproducing in an output circuit thecurrent of a fundamental frequency of a source comprising twotransformers each having firstand second windings, a variableresistance, thefirst windfee the transformer connected to the source.

6. In combination, a source of fundamental frequency, two transformerseach having only first and second windings, an impedance which may befixed at a definite value, and a Variable impedance, the first windingof one of the transformers being connected to the source of fundamentalfrequency, the first winding of the other of the transformers beingconnected to the first mentioned impedance, the second windings of saidtransformers being arranged in a series circuit with the secondmentioned impedance.

7. In combination, a source of fundamental frequency, an output circuit,a transformer having first and second windings, the first winding ofsaid transformer being connected to the source of fundamental frequency,and means for reproducing the fundamental frequency in the outputcircuit through the transformer without introducing harmonics of thefundamental frequency generated by the transformer, said meanscomprising another transformer, a resistance connected to said outputcircuit, and an impedance connected to the first winding of the lattertransformer, the second windings of said transformers being arranged ina series circuit with the resistance.

8. In combination, a source of fundamental frequency, an output circuitfor receiving the fundamental frequency, and means for isolating theoutput circuit from the source of fundamental frequency withoutintroducing the harmonics of the fundamental frequency, said meanscomprising two transformers, each having first and second windings, arheostatconnected to the output circuit, and a variable impedance, thesecond windings of the transformers being arranged in a series circuitwith the rheostat, the first winding of one of the transformers beingconnected to the source of fundamental frequency, the first winding ofthe other of the transformers being connected to the variable impedance.

9. In combination, a source of fundamental frequency, an output circuit,and means for faithfully reproducing the fundamental frequency in theoutput circuit without the introduction of the harmonics of thefundamental frequency, said means comprising two transformers eachhaving first and second windings, the first winding of one of thetransformers being connected to the source of fundamental frequency, andan impedance connected to the first winding of the other of saidtransformers, the second windings of said transformers being connectedin series with the output circuit, one transformer setting up harmonicsof the fundamental frequency due to the impedance associated therewith,which are equal in magnitude and opposite in phase to those set up bythe other transformers due to its connection with the source offundamental fre quency.

10. The method of eliminating the harmonics of a fundamental frequencygenerated in a transformer connected to a source of fundamentalfrequency with a second transformer, each of said transformers havingfirst and second windings, the second windings of said transformersbeing connected in a series circuit with a resistance, which consists ingenerating in the second transformer the same harmonics and adjustingthe harmonics generated in the second transformer so as to be oppositein phase to those generated in the first transformer.

In testimony whereof, I have signed my name to this specification this26th day of February, 1926.

PAUL W. BLYE.

